This invention relates to delivery devices, and in particular to a commercial unit of an apparatus for delivery of pressurized particulate matter against a surface or target to abrade, texture, sandblast, etch, erase, cut, penetrate, smooth, clean, polish, harden and/or deburr the surface or target. The invention is expected to be used largely by hobbyists, although numerous other uses are within the contemplation of the inventors.
The present invention is a refillable fluidizing chamber, cannula and check valve assembly intended for use primarily by hobbyists. It differs significantly in use from the predecessor invention disclosed and claimed in the immediately prior parent application. The latter was a device intended for use by dentists and dental hygienists, and was approved for that use by the FDA. The parent application also differs because it was prefilled, sealed, and disposable to avoid contamination so it would qualify for FDA approval. No such requirements exist for the present invention.
Earlier designs of pressurized particulate matter delivery devices have demonstrated there can be difficulty with clogging in the fluidizing chamber and/or the delivery tube. The present invention is partially directed to an improved internal structure of the fluidizing chamber which produces effective fluidization without clogging.
The invention further provides for a double function check valve feature, that may either of at least three possible configurations. Regardless of which configuration is employed, the first function is to prevent backflow of particulate matter in the event of a drop in pneumatic pressure. The second function is to prevent excessive pressure from reaching the fluidizing chamber and delivery tube in the event of a pressure surge.
The preferred configuration is to employ a duckbill valve in the fluidizing chamber at the end of the inlet tube to prevent backflow in the event of a pressure drop in combination with a single acting flapper valve prior to the fluidizing chamber as a pressure limiting device. The first alternative embodiment is to use a resiliently biased double acting flapper member type check valve in series with the fluidizing chamber to both to close off the pressure source connection to prevent backflow if the pressure drops to a threshold value and also to resist excessive pressure from a pressure source. A second alternative embodiment of the dual function check valve feature is the custom designed double acting mechanical (coil spring biasing) check valve of the immediate predecessor parent invention, which is fully disclosed again herein.
The double function check valve feature, regardless of which configuration is used, is designed to be in fluid communication with a pneumatic pressure line that is operated on and off by a control apparatus that may optionally be in the form of a foot pedal. Since this control apparatus technology is well known, it is not disclosed and is referred to as conventional.
Another feature of the invention includes a disposable cannula that preferably includes a tapered nozzle (which may be really a disposable hypodermic needle) which can be detached from the refillable fluidizing chamber. Detachment is important because the cannula will need to be replaced regularly, since the grit is abrasive and wears out the cannula more quickly than other components in the inventive assembly. Detachment also facilitates optional availability of a plurality of differing tips to accommodate differing grit sizes and different pressure in the fluidizing chamber. Also available are bent particle delivery cannula, which are furnished bent at a 45 degree angle or a 90 degree angle.
Examples of prior known devices include that described in U.S. Pat. No. 4,941,298 to Fernwood, which discloses a rear-reservoir micro sandblaster. The Fernwood patent has numerous problems including costly to dispose, special training for set up and use, and cannot deliver varying sizes of particles. Other known devices with similar problems are the Microetcher(trademark) and the Handiblaster(trademark) available from Mirage/Chameleon Dental Products, Inc.
The primary object of the present invention is to provide a pressurized particulate matter delivery device intended to be used largely by hobbyists that includes a refillable fluidizing chamber, cannula and dual check valve functions. The inventive device provides delivery of pressurized particulate matter against a surface or target to abrade, texture, sandblast, etch, erase, cut, penetrate, smooth, clean, polish, harden and/or deburr the surface or target.
Another important object of the present invention is to provide a particulate matter delivery device that includes an improved internal structure of the fluidizing chamber which produces effective fluidization without clogging.
One more important object of the present invention is to provide a particulate matter delivery device wherein the fluidizing chamber and cannula assembly is in series with a double function check valve feature, the first of which is to prevent excessive pressure from reaching the fluidizing chamber and delivery tube in the event of a pressure surge, and the second is to prevent backflow of particulate matter in the event of a drop in pneumatic pressure.
A related object of the invention is to satisfy the foregoing objective by employing a single acting resiliently biased flapper check valve in series with the fluidizing chamber and a separate duckbill valve in the fluidizing chamber to both resist excessive pressure from a pressure source and prevent backflow in the event of a pressure drop below a threshold value.
A further related object of the invention is to satisfy the foregoing objective by employing a double acting resiliently biased flapper member type check valve in series with the fluidizing chamber to both resist excessive pressure from a pressure source and prevent backflow in the event of a pressure drop below a threshold value.
An alternative related object of the invention is to satisfy the same objective by employing a custom designed double acting safety mechanical check valve.
Another object of the invention includes a disposable cannula, preferably with a tapered nozzle. The cannula can be detached from the refillable fluidizing chamber, in part because the cannula will need to be replaced regularly, since the grit is abrasive and wears out the cannula more quickly than other components in the inventive assembly.
A further related object of the invention is facilitate interchangeable availability and use of a plurality of different cannula tips to accommodate differing grit sizes and different pressure in the fluidizing chamber and to allow use of various bent particle delivery cannula, which are furnished straight, bent at a 45 degree angle or bent at a 90 degree angle.
A further object of this invention is to provide a device for delivery of a fluid particle stream using a cannula with a tapered nozzle to accelerate particle velocity.
An additional object of this invention is to provide a particulate matter delivery apparatus that is lightweight to facilitate convenient use by a hobbyist or other user.
Further objects and advantages of this invention will be apparent from the following detailed description of a presently preferred embodiment which is illustrated schematically in the accompanying drawings.
In accordance with a major aspect of the invention, there is provided an apparatus for delivery of pressurized particulate matter against a surface or target to abrade, texture, sandblast, etch, erase, cut, penetrate, smooth, clean, polish, harden and/or deburr the surface or target. A preferred embodiment thereof includes a refillable fluidizing chamber for mixing fluid and particulate matter together by suspending the latter in the former, and a detachable cannula tube having a particle accelerating tapered nozzle extending outside the fluidizing chamber, wherein the cannula tube delivers pressurized particulate matter from the fluidizing chamber to a surface or target at a high velocity.
The fluidizing chamber incorporates a simple yet extremely effective internal structure to accomplish the suspension of the particulate matter in the fluid, usually air. It is merely comprised of a discharge end of an inlet tube that is disposed below the intake end of the cannula or overlaps it. The effect is that the discharge of the inlet tube blows the particulate matter into the fluid above the intake end of the cannula, thereby suspending it therein, without clogging.
The components of the fluidizing chamber structure are comprised of a tapered barrel, to which the cannula is detachably connected, and a barrel end cap, to which the inlet tube is fixedly inserted. The barrel end cap preferably has external threads which rotate about and engage mateable internal threads inside the top of the barrel of the fluidizing chamber. The barrel end cap includes a refill aperture, which is threaded to accept a removable refill aperture plug. With the plug removed, the fluidizing chamber can be recharged with particulate matter using a filling cartridge, which is preferably equipped with a snap tip and a fill nozzle. This structure allows for the invention to be recharged with particulate matter. In order to accomplish this, it is also necessary to disconnect the top end of the tapered barrel in the form of a locking hub end from a hub end connector that is downstream of the pressure source.
Another important aspect of the preferred embodiment is the double function check valve feature. The first is to prevent backflow of particulate matter in the event of a drop in pneumatic pressure, and the second is to prevent excessive pressure from reaching the fluidizing chamber in the event of pressure surge, such as from a runaway unregulated compressor.
The preferred configuration is to employ a duckbill valve in the fluidizing chamber at the end of the inlet tube to prevent backflow in the event of a pressure drop in combination with a single acting flapper valve prior to the fluidizing chamber as a pressure limiting device. The first alternative embodiment is to use a resiliently biased double acting flapper member type check valve in series with the fluidizing chamber to both to close off the pressure source connection to prevent backflow if the pressure drops to a threshold value and also to resist excessive pressure from a pressure source. A second alternative embodiment of the dual function check valve feature is a custom designed double acting mechanical (coil spring biasing) check valve. The first function is to seal off the pressure source when the pressure drops to a threshold level to prevent backflow of particulate matter into the pressure line.
In the preferred embodiment, the duckbill valve accomplishes this, and the single acting flapper valve is biased into a neutral position so that high pressure will be necessary to close off the fluidizing chamber. In the first alternative embodiment, resilient biasing is used to hold the double acting flapper member in blocking relationship to the exit orifice of the pressure line, since a pressure drop will then permit this blocking function to occur. Put another way it accomplishes this by simply holding the flapper valve against the exit orifice of the pressure line when there is insufficient pressure to resist the biasing force. The second function, preventing excessive pressure from reaching the fluidizing chamber and ultimately the particle stream exiting the cannula is accomplished by the pressure rising to the level that the double acting flapper member is pushed into a blocking relationship with the inlet tube of the fluidizing chamber.
The second alternative embodiment is the custom designed double acting mechanical safety check valve of the immediate predecessor parent invention. It is also disposed between the fluidizing chamber and a pneumatic pressure line. This check valve similarly acts to prevent particulate matter from being drawn back in to the pneumatic pressure line in the event of a sudden drop in pressure, but will also will seal off the inlet tube into the fluidizing chamber in the event of a pressure surge such as may occur with a regulator failure or an unregulated runaway compressor.
Another feature of the invention includes a disposable and replaceable cannula which preferably includes tapered nozzle to accelerate the particulate matter as it exits from the cannula. The cannula may be conventional (really a disposable hypodermic needle). Regardless of its design detail, it must be detachable from the refillable fluidizing chamber. Detachment is important because the cannula will need to be replaced regularly, since the grit is abrasive and wears out the cannula more quickly than other components in the inventive assembly. Detachment also facilitates optional availability of a plurality of differing tips to accommodate differing grit sizes and different pressure in the fluidizing chamber. Also available are bent particle delivery cannula, which are furnished bent at a 45 degree angle or a 90 degree angle. The tapered aspect of the cannula acts as a particle accelerator because it increases the velocity of the particles exiting from the cannula discharge orifice.
The invention is designed to attach to a pneumatic pressure line and is operated on and off by a control apparatus that may optionally be in the form of a foot pedal. The fluidizing chamber and cannula assembly is lightweight and removably connected to the pressure source.